Nanotechnology plays an important role in biomedical applications, which is focused on physical and chemical properties and the properties related to sizes. Optical analysis has been widely used for the protein - receptor interactions, which are of great importance in medical applications. The ability to carry drugs, endogenous and exogenous substances makes albumins very important in medicinal applications. In the present study, the interaction between varying concentrations of Human Serum Albumin and ultra small gold nanoparticles on the fluorescence of fluorescein are studied using dual beam thermal lens technique. For increasing concentrations of albumin, there is an enhancement in fluorescence intensity of fluorescein. High plasmon field created around the nanoparticles increases the excitation decay rate with an increase in radiative efficiency. The enhancement or quenching is determined by the distance between fluorophore and metal nanoparticles. Here Human Serum Albumin acts as a spacing layer between fluorescein molecule and gold nanoparticles. Studies aimed at associate the size, shape, physicochemical functionality, surface charge, and composition of nanomaterials with bio- molecular structure provides groundwork for rational designing of the next-generation nano tools beneficial for advanced biological applications.